Construction of the world’s largest and most energetic laser officially finished today, after more than a decade of hang-ups and controversy and 7 years later than initially planned. The laser will power the $4 billion National Ignition Facility, sited at the Lawrence Livermore National Laboratory in California, which aims to produce fusion by using a blast of laser light to squeeze a tiny capsule of deuterium and tritium to incredibly high pressures and temperatures. But the scientific fun won’t begin just yet: The first attempt to “ignite” fusion won’t take place until sometime next year.
In actuality, the facility has been revving up for some time.
Funded by the U.S. Department of Energy, NIF, as it's called, has already fired with an energy of 1.1 megajoules, more than half of its maximum energy of 1.8 megajoules, NIF Director Edward Moses tells ScienceInsider. That shot was aimed into empty space, but over the coming months, more components of the complex target apparatus will be put in the path of the beams before an attempt will be made to ignite the deuterium-tritium mixture. Ignition signifies the point at which the fusion reaction generates more energy than was put in to make it happen.
NIF was built in large part to maintain the United States’s stockpile of nuclear weapons. Since the United States stopped testing nuclear weapons in 1992, DOE has overseen a program to monitor and maintain the existing stockpile, which includes efforts to develop complex computer simulations of nuclear explosions to better understand them in the absence of real testing. NIF’s role is one of verification: Although it can’t exactly simulate the conditions in a thermonuclear explosion, it should provide real data to show that the predictions of the computer simulations are on the right track. Weapons-related experiments don’t all require ignition, but achieving that condition would open new regimes in which simulations can be tested.
But in the minds of the public—and of Congress, which funded the project—ignition is the real test of NIF’s worth. Using lasers to squeeze a tiny capsule of fuel to conditions more extreme than those that exist in the sun is a devilishly complex task that will take just as much ingenuity as has been expended building the laser in the first place. If NIF gets there, it will be a triumph for fusion research but still a very long way from building a fusion power station.